The present invention relates to a method of making a laminate, comprising: providing a plastics material mesh structure such as a grid or geogrid or a net having oriented strands connected together by thicker and non-oriented or less-oriented portions; providing a fabric for lamination to the mesh structure; heating the surfaces of said thicker portions to soften or melt the surfaces; passing the mesh structure and the fabric through a nip formed by a nip member and a backing member, to cause the softened or melted plastics material of said thicker portions to penetrate into the fabric; and cooling the laminate so formed. The invention also relates to the laminate itself and to the laminating machine.
Such a method and laminate are described in U.S. Pat. No. 5,152,633 (Mercer et al). In the procedure described, the mesh structure and the fabric are passed between two rollers which provide an initial nip. There is however a tendency for the rollers to squeeze the plastics material backwards away from its initial position by what can be termed the "cherry stone effect". This reduces the thickness of the plastics material available for penetration into the fabric and reduces the strength of the bond between the mesh structure and the fabric.
In the procedure shown in U.S. Pat. No. 5,152,633, the heat is applied to the mesh structure through the fabric, and the danger of shrinking the fabric is avoided by choosing a fabric with a higher softening or melting temperature than the surfaces of said thicker portions. However, it is in certain cases desirable to use a fabric with a similar or lower softening or melting temperature than that of said surfaces.
The oriented strands of the mesh structure should not be heated so much that they de-orient; for some applications such as reinforcing asphalt, it is undesirable that the strands should adhere to the fabric.
The expression "soften or melt" is used herein. Plastics materials soften very significantly before their melting point and may have an indefinite melting point. It is not essential that the plastics material be molten in order to penetrate into the fabric, though it is understood that it must be sufficiently soft.